See:
http://www.flightglobal.com/articles/2008/01/22/221030/grob-to-build-learjet-85-all-composite-airframe.html
and
http://www.asd-network.com/press_detail_B.asp?ID=14840&NID=241073
... apparently Airfix have yet to confirm or deny that they've been retained on a consultancy basis for the project.